The present invention relates to clamping sleeves by means of which a tool or a workpiece with a cylindrical clamping surface can be clamped in a machine for driving the tool or workpiece. The clamping sleeve has a truncated conical surface, which is intended to be tightened against a corresponding conical surface of the machine, e.g. in a chuck or conical pin driven by the machine spindle.
Such previously known sleeves have usually the shape of a homogeneous body with a truncated conical outside and a substantially cylindrical hole or, depending on the use, instead a substantially cylindrical outside and a truncated conical hole. Moreover, the body is provided with a number of axial slits extending alternatingly from each end.
In use the sleeve with adapted tool or workpiece is tightened against the driven conical surface. However, in order that the gripping force about the tool and the workpiece, respectively, should be enough, it is necessary to press the clamping sleeve axially onto the conical surface by a nut which can be axially screwed onto the driven chuck or pin. The sleeve is clamped to the tool or workpiece by its "resilient properties" and its axial displacement along the conical surface and will lock the tool or workpiece to the chuck or pin.
The clamping ability of the sleeve is directly dependent on the frictional conditions existing between the sleeve and chuck-body in the axial and tangential direction. The lower the friction is, the greater the clamping force must be, but at the same time the joint will be less stable especially as it is subjected to vibrations.
The accuracy of the consecutive working of a slitted sleeve is dependent on the peripheral elongations to which it is exposed when tightened. As the frictional conditions vary, e.g. a slit containing a burr, varying lubrication, etc, unsymmetrical frictional conditions with varying elongations along the periphery will be the consequence, and the final result is a bad accuracy of consecutive working. There is also a risk that partial elongations will be so great that a permanent tension occurs with a consequent deteriorated accuracy of the relative sleeve.
Thus, this known sleeve has essential shortcomings, and so far it has not been possible to avoid these.
This essential and so far unsolved problem of the present sleeve of the type intended here is eliminated by the present invention. The influence of varying friction is reduced with the sleeve of the invention, the elongations take place radially and symmetrically due to the "hydrostatic paradox". The result will be a better clamping force and accuracy of consecutive working meaning an improved accuracy as well as clamping force and reduced wear.